This thing was dropped off at my house today. It was a fish finder but it looks to me like he somehow hooked it up backwards. I spotted this as soon as I opened it up, right in front of the power connections.

 

What is it you see in those pictures? I see some bad soldering.

Who is “he” and what is “hooked up backwards?”

 

What is it you see in those pictures? I see some bad soldering.

Who is “he” and what is “hooked up backwards?”

He is a friend and he hooked up the fish finder with 24 Volts backwards he attempted to fix the power cable into the device and when he brought it to me I saw that the red wire was attached to the black wire and then he hooked the thing up. Maximum voltage according to the manufacturer is recommended 12V but not to exceed 20V. 24volts hooked into the power rail backwards took out that inductor and it looks like the 2caps right by it. Further along that same track there are a couple of transistors not reading correctly in circuit or out. there is no schematic for the unit anywhere so tracing down the problem is way beyond what I wish to do. I don't think it can easily be fixed. forgetting the fact that it's all SMD parts and there is a processor also fed by that 12 volt line and it could also be effected. that black bubble in the photo used to be an inductor and it's twin I think on the other side. together I think they form a protection circuit on the input. but he exceeded the design expectations of the maker.

 

Okay. So what is it he is expecting you to do? Fix it?

Tell your friend to get another one and consider the cost of this one tuition for a valuable lesson (also known as stupid tax), namely don't apply power to things backwards.

 

Okay. So what is it he is expecting you to do? Fix it?

Tell your friend to get another one and consider the cost of this one tuition for a valuable lesson (also known as stupid tax), namely don't apply power to things backwards.

And not at double the specified voltage.

 

And not at double the specified voltage.

Yea that's what I told him. He asked me to try so I took it apart and looked at the damage and said you need a new one. If I could find schematics for it I may just give it a shot. but the company never produced a public schematic for the unit and much of the design is proprietary and I'm not an engineer so reverse engineering is out of my ballpark. So I am not even going to try.